In the semiconductor industry, IC chips or dice are typically fabricated in flat wafers having diameters of several inches. Each wafer contains hundreds of chips which are individually tested before the wafer is scribed to separate the chips for further assembly.
Such testing is conducted by means of a prober unit which usually includes a base plate with an opening therein, a movable chuck located beneath the base plate opening, a microscope positioned above the base plate opening, together with associated testing circuitry and controls. The wafer of dice to be tested is secured to the chuck which is selectively movable in a vertical direction along the Z axis as well as in a horizontal direction along the X and Y axes. A generally circular probe card having multiple probes terminating in a predetermined pattern corresponding to the contacts on the chips is positioned within the base plate opening for rotational movement in a .theta. direction about the Z axis. In manual prober units, relative movement between the probe card and wafer is controlled by the operator. In automatic prober units, it is controlled by motors and a programmable microprocessor. An ink jet is usually provided to selectively spray the chip being tested.
The probe card and test circuitry are electrically interconnected by a multipin coupler which typically has included a lower portion fixed to the probe card and an upper portion fixed to a movable housing enclosing the test circuitry. After the probe card and wafer have been aligned, which is done by the operator looking through the microscope with the aid of spaced apart dummy chips on the wafer, the X, Y and Z increments necessary to step from chip to chip are then programmed into the microprocessor controlling the motorized chuck so that the chips can individually be brought into precise engagement with the probe card for testing. Those chips which test bad are marked with the ink jet.
Several difficulties have been encountered with the multipin couplers of the prior art. The couplers available heretofore have contributed some inaccuracies to the testing operation by reason of the variable impedances accompanying electrical connections of different lengths between the probe card and test circuitry. It will be appreciated that numerous leads are necessary to interconnect the probe card and test circuitry. In addition, since it is often necessary to disconnect the coupler during testing of a wafer in order to clean the probes on the probe card, clear the ink jet, etc., it is important that such be accomplished without disturbing and thus misaligning the probe card. It will be appreciated that a misaligned probe card can damage or destroy dice and requires realignment, which can be time consuming and thus expensive. Further, the couplers of the prior art have configurations which interfere with the operator's view of the wafer during probing and do not adequately provide either for adjustability or alignment between the coupler portions to avoid damaging the pins upon reconnection.
A need thus exists for a new and improved multipin coupler for interconnecting the probe card and test circuitry of a semiconductor chip test prober unit.